Proetida is an order of

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

that lived from the

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

to the

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

. It was the last order of trilobite to go extinct, finally dying out in the Permian-Triassic extinction event.

Description

These typically small trilobites resemble those of the order

Ptychopariida Ptychopariida is a large, heterogeneous order of trilobite containing some of the most primitive species known. The earliest species occurred in the second half of the Lower Cambrian, and the last species did not survive the Ordovician–Silurian ...

, from which the new order Proetida was separated in 1975 by Fortey and Owens. Like the order

Phacopida Phacopida ("lens-face") is an order of trilobites that lived from the Late Cambrian to the Late Devonian. It is made up of a morphologically diverse assemblage of taxa in three related suborders. Characteristics Phacopida had 8 to 19 thoraci ...

, the proetids have

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton (endoskeleton) in for example, a human. In usage, some of the ...

s that sometime have pits or small tubercles, especially on the

glabella The glabella, in humans, is the area of skin between the eyebrows and above the nose. The term also refers to the underlying bone that is slightly depressed, and joins the two brow ridges. It is a cephalometric landmark that is just superior to ...

(middle portion of the head). Because of their resemblance to the

in some features, the proetids are included in the subclass Librostoma. Unlike the trilobites of the phacopid suborder

Phacopina The Phacopina comprise a suborder of the trilobite order Phacopida. Species belonging to the Phacopina lived from the Lower Ordovician ( Tremadocian) through the end of the Upper Devonian (Famennian).Moore, R.C. (ed.). Treatise on Invertebrate Pal ...

, whose eyes are schizochroal, the proetids have the more common

holochroal eye Holochroal eyes are compound eyes with many tiny lenses (sometimes more than 15,000, each 30-100μm, rarely larger). They are the oldest and most common type of trilobite eye, and found in all orders of trilobite from the Cambrian to the Permian ...

s. These eyes are characterized by close packing of biconvex

lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

beneath a single

cornea The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Along with the anterior chamber and lens, the cornea refracts light, accounting for approximately two-thirds of the eye's total optical power ...

l layer that covers all of the lenses. Each lens is generally hexagonal in outline and in direct contact with the others. They range in number from one to more than 15,000 per eye. Eyes are usually large, and because the individual lenses are hard to make out, they look smooth and sometimes bead-like. The

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

of proetids was made up of anywhere between 8–22 segments, but most commonly 10. Many also extend the backcorners of the headshield into so-called genal spines. These two features can aid in distinguishing proetids from some phacopid trilobites in the suborder

, to which they can be very similar.

Classification

Opinions about the composition of and the affinities within the proetids, and to other trilobites, have been very divergent over time. In 2011 it was suggested to retain in Proetida only the families Proetidae and Tropidocoryphidae. The remainder of the families should be combined in a new proposed order, Aulacopleurida (Adrian, 2011), that would consist of the families Aulacopleuridae, Brachymetopidae, Dimeropygidae, Rorringtoniidae, Scharyiidae, Bathyuridae, Telephinidae, Holotrachelidae and Hystricuridae (considered Proetida before), combined with the Ptychopariid families Alokistocaridae, Crepicephalidae, Ehmaniellidae, Marjumiidae, Solenopleuridae and Tricrepicephalidae. The reasoning for this proposed split is based on differences in early larval stages. While the remaining Proetida taxa have globular larvae very unlike the adult form, the Aulacopleurids have adultlike larvae with paired spines. Others observe that globular non-adult larvae also occur in some taxa within the proposed order Aulacopleurida. More recently

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis of both larval and adult characters suggests the proetids as earlier understood probably are

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

. Two larval characters are unique to all Proetida; the first is that the eye develops on the side of the headshield, not at the front, and the second is a forwardly tapering

that is distanced from the rim of the headshield. The analysis identifies the taxa

Asaphida Asaphida is a large, morphologically diverse order of trilobites found in marine strata dated from the Middle Cambrian until their extinction during the Silurian. Asaphida contains six superfamilies (Anomocaroidea, Asaphoidea, Cyclopygoidea, ...

Olenina ''Olenina'' is an extinct suborder of the trilobite order Ptychopariida. Subdivisions *Superfamily Olenoidea **Family Ellipsocephaloididae **Family Olenidae Olenidae is a family of ptychopariid trilobites. Some genera, '' Balnibarbi'' and ...

and

(including the Holotrachelidae) as sister groups. The earliest branch in Proetida is the family Hystricuridae. This is followed by a branch that consists of the families Dimeropygidae and Toernquistiidae. At the third node, the superfamily Aulacopleuroidea (consisting of Aulacopleuridae and Brachymetopidae) split off. The fourth branch is the family Scharyiidae. The fifth branch consists of the families Roringtoniidae and Tropidocoryphidae. The sixth node combines a restricted Bathyuridae split off from ''Bathyurella'' with the family Proetidae (including Phillipsiidae, which, according to Lamsdell, has been demoted to the subfamily Phillipsiinae).

Taxonomy

The following superfamilies, families and genera are recognized:

Superfamily Aulacopleuroidea

Family Aulacopleuridae *''

Aulacopleura ''Aulacopleura'' is a genus of proetid trilobite that lived from the Middle Ordovician to the Middle Devonian. Some authors may classify this group as subgenus ''Otarion (Aulacopleura)''. The cephalon is semicircular or semielliptical, with bord ...

'' *'' Aulacopleuroides'' *'' Beggaspis'' *''

Chamaeleoaspis ''Chamaeleoaspis'' is a genus of tiny trilobites found in Early to Middle Eifelian marine strata of Africa and Europe. The two species look very similar to the trilobites of the related genera ''Cyphaspis'' and '' Otarionella'', in which the spec ...

'' *'' Coignops'' *'' Cyphaspides'' *''

Cyphaspis ''Cyphaspis'' is a genus of small trilobite that lived from the Late Ordovician to the Late Devonian. Fossils have been found in marine strata in what is now Europe, Africa and North America. Various species had a compact body, and a large, bul ...

'' *'' Dixiphopyge'' *'' Harpidella'' *'' Latecephalus'' *'' Malimanaspis'' *'' Maurotarion'' *'' Namuropyge'' *'' Otarion'' *'' Otarionides'' *'' Protocyphaspides'' *'' Pseudotrinodus'' *'' Songkania'' *'' Tilsleyia'' Family Brachymetopidae *'' Acutimetopus'' *'' Asiagena'' *'' Australosutra'' *'' Brachymetopella'' *'' Brachymetopus'' *'' Cheiropyge'' *'' Conimetopus'' *'' Cordania'' *'' Eometopus'' *'' Loeipyge'' *'' Mystrocephala'' *'' Proetidea'' *'' Radnoria'' *'' Spinimetopus'' Family Rorringtoniidae *'' Cyamella'' *'' Hanjiangaspis'' *'' Isbergia'' *'' Madygenia'' *'' Protarchaeogonus'' *'' Rorringtonia'' *'' Solariproetus''

Superfamily Bathyuroidea

Family Bathyuridae *'' Acidiphorus'' *'' Aksuaspis'' *'' Aponileus'' *'' Bathyurellus'' *'' Bathyurus'' *'' Benthamaspis'' *'' Bolbocephalus'' *'' Catochia'' *'' Ceratopeltis'' *'' Eleutherocentrus'' *'' Ermanella'' *'' Gignopeltis'' *'' Grinnelaspis'' *'' Hadrohybus'' *'' Jeffersonia'' *'' Licnocephala'' *'' Lutesvillia'' *'' Madaraspis'' *'' Peltabellia'' *'' Petigurus'' *'' Platyantyx'' *?'' Proscharyia'' *'' Psephosthenaspis'' *'' Pseudoolenoides'' *'' Punka'' *'' Rananasus'' *'' Randaynia'' *'' Raymondites'' *'' Sinobathyurus'' *'' Strigigenalis'' *'' Uromystrum'' Family Dimeropygidae (including Celmidae) *'' Celmus'' *'' Dimeropyge'' *'' Dimeropygiella'' *'' Glaphurella'' *'' Ischyrotoma'' *'' Pseudohystricurus'' Family Holotrachelidae *'' Holotrachelus'' *'' Kinderlania'' Family Hystricuridae *'' Amblycranium'' *'' Etheridgaspis'' *'' Flectihystricurus'' *'' Genalaticurus'' *'' Glabretina'' *'' Guizhouhystricurus'' *'' Hillyardina'' *'' Hintzecurus'' *?'' Holubaspis'' *'' Hyperbolochilus'' *'' Hystricurus'' *'' Ibexicurus'' *'' Lavadamia'' *'' Nyaya'' *'' Omuliovia'' *'' Pachycranium'' *'' Paenebeltella'' *'' Parahystricurus'' *'' Paraplethopeltis'' *'' Politicurus'' *'' Psalikilopsis'' *'' Psalikilus'' *'' Rollia'' *'' Rossicurus'' *'' Tanybregma'' *?'' Taoyuania'' *'' Tasmanaspis'' *'' Tersella'' Family Raymondinidae (including Glaphuridae) *'' Glaphurina'' *'' Glaphurus'' *'' Raymondina'' *'' Tagazella'' *'' Varanella'' Family

Telephinidae Telephinidae is a family of pelagic trilobites with large wide-angle eyes, occupying most of the free cheeks, downward directed facial spines and 9-10 thorax segments. The family is known during the entire Ordovician and occurred in deep water ar ...

*''

Carolinites ''Carolinites'' is a genus of trilobite, assigned to the Telephinidae family, that occurs during the Lower and Middle Ordovician. ''Carolinites'' had a pantropical distribution, and there is evidence that it lived in upper parts of the water co ...

'' *'' Fialoides'' *'' Goniophrys'' *'' Oopsites'' *'' Opipeuterella'' *'' Paraphorocephala'' *'' Phorocephala'' *?'' Pyraustocranium'' *'' Telephina'' *'' Telephops'' Family Toernquistiidae *'' Chomatopyge'' *'' Mesotaphraspis'' *'' Toernquistia'' *?'' Toernquistina''

Superfamily Proetoidea

Family Phillipsiidae *'' Acanthophillipsia'' *'' Acropyge'' *'' Ameropiltonia'' *'' Ameura'' *'' Ampulliglabella'' *'' Anisopyge'' *'' Archegonus'' *'' Bedicella'' *'' Breviphillipsia'' *'' Carbonocoryphe'' *'' Cummingella'' *'' Delaria'' *'' Ditomopyge'' *'' Doublatia'' *'' Griffithidella'' *'' Griffithides'' *'' Grossoproetus'' *'' Hentigia'' *'' Hesslerides'' *'' Hildaphillipsia'' *'' Iranaspidion'' *'' Jimbokranion'' *'' Kollarcephalus'' *'' Microphillipsia'' *'' Neoproetus'' *'' Nipponaspis'' *'' Novoameura'' *'' Nunnaspis'' *'' Paraphillipsia'' *''Persia'' *'' Phillibole'' *''Phillipsia'' *'' Piltonia'' *'' Pseudophillipsia'' *'' Simulopaladin'' *'' Spinibole'' *'' Thaiaspis'' *'' Thigriffides'' *'' Timoraspis'' *'' Triproetus'' *'' Vidria'' *'' Weania'' Family

Proetidae Proetidae is a family of proetid trilobites. The first species appeared in the Upper Ordovician, and the last genera survived until the Middle Permian. However, if the closely related family Phillipsiidae is actually a subfamily of Proetidae, t ...

*'' Aayemenaytcheia'' *'' Aceroproetus'' *'' Alaskalethe'' *'' Altajaspis'' *'' Anambon'' *'' Anglibole'' *'' Angustibole'' *'' Anujaspis'' *'' Appendicysta'' *'' Aprathia'' *'' Archaeocoryphe'' *'' Ascetopeltis'' *'' Astroproetus'' *'' Australokaskia'' *'' Bailielloides'' *'' Bapingaspis'' *'' Basidechenella'' *'' Beleckella'' *'' Belgibole'' *'' Benesovella'' *'' Bitumulina'' *'' Blodgettia'' *'' Bohemiproetus'' *'' Bolivicrania'' *'' Boliviproetus'' *'' Bollandia'' *'' Bonnaspidella'' *''Borealia'' *'' Brevibole'' *'' Burgesina'' *'' Calybole'' *'' Camsellia'' *'' Carbonoproetus'' *'' Carlopsia'' *'' Carniphillipsia'' *'' Ceratoproetus'' *'' Chauffouraspis'' *'' Chaunoproetoides'' *'' Chaunoproetus'' *'' Chiides'' *'' Chiops'' *'' Chlupacula'' *'' Chuanqianoproetus'' *'' Clavibole'' *'' Comptonaspis'' *'' Coniproetus'' *'' Conophillipsia'' *''Constantina'' *'' Coombewoodia'' *'' Craspedops'' *'' Crassibole'' *'' Crassiproetus'' *'' Cyphinioides'' *'' Cyphoproetus'' *'' Cyrtodechenella'' *'' Cyrtoproetus'' *'' Cyrtosymbole'' *'' Cystispina'' *'' Daihuaia'' *'' Dayinaspis'' *'' Dechenella'' *'' Dechenelloides'' *'' Dechenellurus'' *'' Deinoproetus'' *'' Deltadechenella'' *'' Diabole'' *'' Diacoryphe'' *'' Drevermannia'' *'' Dudu'' *'' Dushania'' *'' Effops'' *'' Ejinoproetus'' *'' Elegenodechenella'' *'' Elimaproetus'' *'' Elliptophillipsia'' *''

Endops ''Endops yanagisawai'' is a proetid trilobite belonging to the family Proetidae, endemic to Middle Permian-aged marine strata in Fukushima Prefecture, Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country i ...

'' *'' Engelomorrisia'' *'' Ensecoryphe'' *'' Eocyphinium'' *'' Eocyrtosymbole'' *'' Eodrevermannia'' *'' Eomicrophillipsia'' *'' Eopalpebralia'' *'' Eosoproetus'' *'' Eowinterbergia'' *'' Erbenaspis'' *'' Erbenites'' *'' Evagena'' *'' Exochops'' *'' Flexidechenella'' *'' Formonia'' *'' Francenaspis'' *'' Franconicabole'' *'' Frithjofia'' *'' Fuscinipyge'' *'' Ganinella'' *'' Gapeevella'' *'' Geigibole'' *'' Georhithronella'' *'' Gerastos'' *'' Gitarra'' *'' Globusia'' *'' Globusiella'' *'' Globusoidea'' *'' Gomiites'' *'' Gracemerea'' *'' Hassiabole'' *''

Hedstroemia The extinct genus ''Hedstroemia'' was once thought to be a rivulariacean cyanobacterium. It forms oval blobs composed of sinuous tubes that have rounded outlines and occurs in conjunction with '' Solenopora''. ''Hedstroemia'' was formerly assi ...

'' *'' Helioproetus'' *'' Helmutia'' *'' Helokybe'' *'' Humeia'' *'' Humilogriffithides'' *'' Hunanoproetus'' *'' Hypaproetus'' *'' Jinia'' *'' Karginella'' *'' Kaskia'' *'' Kathwaia'' *'' Kerpenella'' *'' Khalfinella'' *'' Kolymoproetus'' *'' Kosovoproetus'' *'' Krambedrysia'' *'' Kulmiella'' *'' Kulmogriffithides'' *'' Lacunoporaspis'' *'' Laevibole'' *'' Langgonbole'' *'' Latibole'' *'' Latiglobusia'' *'' Latiproetus'' *'' Lauchellum'' *'' Lichanocoryphe'' *'' Linguaphillipsia'' *'' Liobole'' *'' Liobolina'' *'' Longilobus'' *'' Longiproetus'' *'' Lophiokephalion'' *'' Lugalella'' *'' Luojiashania'' *'' Macrobole'' *'' Mahaiella'' *'' Malayaproetus'' *'' Malchi'' *'' Mannopyge'' *'' Megaproetus'' *'' Menorcaspis'' *'' Merebolina'' *'' Metaphillipsia'' *''Mezzaluna'' *'' Microspatulina'' *'' Mirabole'' *'' Monodechenella'' *'' Moravocoryphe'' *'' Moschoglossis'' *'' Myoproetus'' *'' Namuraspis'' *'' Neogriffithides'' *'' Neokaskia'' *'' Nitidocare'' *'' Nodiphillipsia'' *'' Oehlertaspis'' *'' Oidalaproetus'' *'' Orbitoproetus'' *'' Ormistonaspis'' *'' Omlistonia'' *'' Ormistoniella'' *'' Osmolskia'' *'' Otodechenella'' *''

Paladin The Paladins, also called the Twelve Peers, are twelve legendary knights, the foremost members of Charlemagne's court in the 8th century. They first appear in the medieval (12th century) ''chanson de geste'' cycle of the Matter of France, where ...

'' *'' Palaeophillipsia'' *'' Paleodechenella'' *'' Palpebralia'' *'' Panibole'' *'' Parachaunoproetus'' *'' Paradechenella'' *'' Parafrithjofia'' *'' Paraglobusia'' *'' Paragriffithides'' *'' Paramirabole'' *'' Parangustibole'' *'' Parapalpebralia'' *'' Paraproetus'' *'' Parawarburgella'' *'' Particeps'' *'' Parvidumus'' *'' Paryfenus'' *'' Pedinocoryphe'' *'' Pedinodechenella'' *'' Perexigupyge'' *'' Perliproetus'' *'' Phillibolina'' *'' Philliboloides'' *'' Phyllaspis'' *'' Planilobus'' *'' Planokaskia'' *'' Plesiowensus'' *'' Podoliproetus'' *'' Pontipalpebralia'' *'' Praedechenella'' *'' Pragoproetus'' *'' Prantlia'' *'' Prodiacoryphe'' *'' Proetocephalus'' *''

Proetus In Greek mythology, Proetus (; Ancient Greek: Προῖτος ''Proitos'') may refer to the following personages: * Proetus, king of Argos and Tiryns, son of Abas and twin brother of Acrisius. *Proetus, a prince of Corinth as the son of Prince ...

'' *'' Pseudobollandia'' *'' Pseudocyrtosymbole'' *'' Pseudodechenella'' *'' Pseudodudu'' *'' Pseudogerastos'' *'' Pseudoproetus'' *'' Pseudosilesiops'' *'' Pseudospatulina'' *'' Pseudowaribole'' *'' Pudoproetus'' *'' Pulcherproetus'' *'' Pusillabole'' *'' Raerinproetus'' *'' Reediella'' *'' Rhenocynproetus'' *'' Rhenogriffides'' *'' Richterella'' *'' Rijckholtia'' *'' Rosehillia'' *'' Rugulites'' *'' Schaderthalaspis'' *'' Schizophillipsia'' *'' Schizoproetina'' *'' Schizoproetoides'' *'' Schizoproetus'' *'' Semiproetus'' *'' Sevillia'' *'' Silesiops'' *'' Simaproetus'' *'' Sinobole'' *'' Sinocyrtoproetus'' *'' Sinopaladin'' *'' Sinoproetus'' *'' Sinosymbole'' *'' Skemmatocare'' *'' Skemmatopyge'' *'' Spatulata'' *'' Spergenaspis'' *'' Spinibolops'' *'' Struveproetus'' *'' Sulcubole'' *'' Tawstockia'' *'' Taynaella'' *'' Tcherkesovia'' *'' Tetinia'' *'' Thaiaspella'' *'' Thalabaria'' *'' Thebanaspis'' *'' Tropidocare'' *'' Tschernyschewiella'' *'' Typhloproetus'' *'' Unguliproetus'' *'' Vandergrachtia'' *'' Vittaella'' *'' Wagnerispina'' *'' Waideggula'' *'' Waigatchella'' *'' Warburgella'' *'' Waribole'' *'' Weberiphillipsia'' *'' Westropia'' *'' Weyeraspis'' *'' Winiskia'' *'' Winterbergia'' *'' Witryides'' *'' Xenadoche'' *'' Xenoboloides'' *'' Xenocybe'' *'' Xenodechenella'' *'' Xiangzhongella'' *'' Xiushuiproetus'' *'' Yanshanaspis'' *'' Yichangaspis'' *'' Yishanaspis'' *'' Yuanjia'' *'' Zhegangula'' *'' Zhejiangoproetus'' Family Tropidocoryphidae *'' Alberticoryphe'' *'' Astycoryphe'' *'' Bojocoryphe'' *'' Buchiproetus'' *'' Centriproetus'' *'' Cornuproetus'' *'' Cyrtosymboloides'' *'' Dalarnepeltis'' *'' Dalejeproetus'' *'' Decoroproetus'' *'' Denemarkia'' *'' Diademaproetus'' *'' Dipharangus'' *'' Eopiriproetus'' *'' Erbenicoryphe'' *'' Eremiproetus'' *'' Galbertianus'' *'' Gracilocoryphe'' *'' Gruetia'' *'' Guilinaspis'' *'' Ignoproetus'' *'' Interproetus'' *'' Koneprusites'' *'' Krohbole'' *'' Lardeuxia'' *'' Laticoryphe'' *'' Lepidoproetus'' *'' Linguaproetus'' *'' Lodenicia'' *'' Longicoryphe'' *'' Macroblepharum'' *'' Miriproetus'' *'' Nagaproetus'' *'' Paraeremiproetus'' *'' Paralardeuxia'' *'' Paralepidoproetus'' *'' Parvigena'' *'' Perakaspis'' *'' Phaetonellus'' *'' Phaseolops'' *'' Piriproetoides'' *'' Piriproetus'' *'' Pribylia'' *'' Prionopeltis'' *'' Prodrevermannia'' *'' Proetina'' *'' Proetopeltis'' *'' Pterocoryphe'' *'' Pteroparia'' *'' Quadratoproetus'' *'' Rabuloproetus'' *'' Ranunculoproetus'' *'' Remacutanger'' *'' Richteraspis'' *'' Rokycanocoryphe'' *'' Sculptoproetus'' *'' Slimanella'' *'' Spinoproetus'' *'' Stenoblepharum'' *'' Tafilaltaspis'' *'' Tropicoryphe'' *'' Tropidocoryphe'' *'' Vicinoproetus'' *'' Voigtaspis'' *'' Wolayella'' *'' Xiphogonium'' *'' Zetaproetus''

References

{{Taxonbar, from=Q1934211 Trilobite orders Early Ordovician first appearances Lopingian extinctions Taxa named by Richard Fortey